This invention relates generally to airborne targets used to simulate jet aircraft and particularly to airborne targets which produce an exhaust plume for use as a target for missiles and anit-aircraft shells having infrared detectors that respond to the infrared frequencies emitted by, and dimensions of the exhaust plume of a jet engine to follow or locate a target.
It is well known that aerial targets either towed by aircraft or mounted to the wing of the aircraft drones should simulate the characteristics of the aircraft against which anti-aircraft shells and missiles might be used. The exhaust plume is a distinctive characteristic of jet engines that infrared target seekers use to guide missiles toward an aircraft or to cause infrared-detecting shells to detonate. An effective target seeker must distinguish between actual jet aircraft engine plumes and decoy flares that are often released in attempts to divert warheads harmlessly away from an intended target. Note that decoy flares do not produce an exhaust plume having equivalent dimensions or equivalent infrared light emitting characteristics to those of jet aircraft engine. Therefore, a practice target should closely emulate the dimensions of, and spectral distribution of infrared light emitted by the exhaust plume of a jet engine to permit both testing and practice with anti-aircraft weapons.
Aerial targets for emulating jet engines ordinarily burn jet fuel, either JP4 or JP5, and include a combustor comprising one or more pyrotechnic igniters for igniting a fuel-air mixture. The purpose of the combustor is to simulate the jet exhaust by producing an exhaust plume closely matching the characteristics of a jet aircraft engine exhaust plume. The targets are controlled from a station on an aircraft or on the ground so that as the target comes within range of an anti-aircraft weapon, a nozzle in the combustor emits a fine spray of fuel, and an igniter is actuated to initiate combustion. An igniter generally is usable only once. A target may pass within range of a missile or gunnery station several times in a single flight of the towing aircraft.
Previous jet exhaust simulators require that at each pass, an additional igniter is expended to produce a plume for the target seeker and the plume is extinguished as the aerial target moves out of range in order to conserve fuel. When all of the igniters are expended, the targets become useless for infrared target seeker testing and practice since the plume may no longer be relit.
Previous jet exhaust simulators have additional disadvantages, including difficulties with igniting the fuel using igniters at high speeds and high altitudes. Such previous jet exhaust simulators also often fail to produce plumes that accurately represent the dimensions and infrared light spectral distributions of jet engine exhaust plumes. PG,4
Accordingly, there is a need for a target jet exhaust simulator that provides a plume at high speeds and high altitudes and which closely emulates that of jet aircraft engines and which does not require a plurality of pyrotechnic igniters whenever it is desired to actuate the target simulator several times during a single flight of the towing aircraft.